Piston and rod assembly

ABSTRACT

A single split ring retainer is cooperable with abutments on a rod encircled thereby and with other abutments on an annular piston seated on the rod to establish an axial thrust transmitting connection between the piston and rod. The thrust transmitting connection is maintained effective only as long as the retainer is held against lateral displacement from the rod by the wall of the cylinder for which the assembly is intended.

United States Patent Thompson [15] 3,654,839 51 Apr. 11, 1972 [54]PISTON AND ROD ASSEMBLY [72] Inventor:

[73] Assignee: Koehring Company, Milwaukee, Wis.

[22] Filed: Mar. 6, 1970 [21] Appl. No.: 17,125

Glenn S. Thompson, Brown Deer, Wis.

[52] U.S. Cl ..92/200, 92/256 [51] Int. Cl ..F0lb 13/04 [58] Field ofSearch ..92/198, 200, 244, 255, 256,

[56] References Cited UNITED STATES PATENTS 3,426,656 2/1969 Bimba..92/255 3,426,657 2/1969 Bimba... 1,232,305 7/1917 Heft 2,452,83211/1948 Carter ..277/178 3,066,001 1 l/ 1962 Zimmerman ..92/2443,165,032 1/1965 Konkle ..92/252 3,233,907 2/1966 Stanton.. ..277/1783,457,842 7/1969 Tennis ..92/256 Primary Examiner-Martin P. SchwadronAssistant Examiner-Ronald H. Lazarus Attorney-Ira Milton Jones [57]ABSTRACT A single split ring retainer is cooperable with abutments on arod encircled thereby and with other abutments on an annular pistonseated on the rod to establish an axial thrust transmitting connectionbetween the piston and rod. The thrust transmitting connection ismaintained effective only as long as the retainer is held againstlateral displacement from the rod by the wall of the cylinder for whichthe assembly is intended.

5 Claims, 7 Drawing Figures PATENTEDAPR 1 1 I972 SHEET 1 [1F 2 FIGJ. I7) INVENTOR Glenn 5. T ITZJUSUH AT-roRN ATENTEflAPR 11 I972 3,654,839

sum 2 or 2 INVENTOR Zezmfiv". Thum jsun BY ATTOR EY PISTON AND RODASSEMBLY BACKGROUND OF THE INVENTION This invention relates to pistonand rod assemblies for hydraulic cylinders and the like, wherein anannular piston encircles the rod and has an axial thrust transmittingconnection therewith designed to obviate the need for screw threadedfastening means such as were commonly used for that purpose in the past.

An example of that type of piston and rod assembly can be found in theUS. Pat. to F. H. Tennis, No. 3,457,842, issued July 29, 1969. Astherein disclosed, a plurality of split rings encircling the rod withinner portions confined in axially spaced circumferential grooves in therod and outer portions abutting the opposite ends of the piston wereprovided to drivingly connect the latter to the rod. The wall of acylinder containing the assembly was alone relied upon to hold the splitrings against lateral displacement from the rod.

SUMMARY OF THE INVENTION The purpose of this invention is to providesimplified and improved means for establishing an axial thrusttransmitting connection between an annular piston and a piston rodencircled thereby without entailing the use of tools or relying uponscrew threaded means of any kind; and its object is to achieve that endthrough the employment of but a single split ring interconnected withthe rod and thepiston in a way that does not interfere with lateraldisplacement of the ring from the rod whenever it is free of therestraint placed upon it by the wall of the cylinder for which theassembly is intended.

With these observations and objects in mind, the manner in which theinvention achieves its purpose will be appreciated from the followingdescription and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view partially inelevation and partly in longitudinal section of a portion of a cylinderequipped with a piston and rod assembly of this invention;

FIG. 2 is a cross sectional view taken through FIG. 1 on the line 2-2,with portions broken away to show underlying structure;

FIG. 3 is a perspective view, on a reduced scale, of the split ring typepiston retainer employed in FIGS. 1 and 2, but with its component partsseparated;

FIG. 4 is a view similar to FIG. 1, illustrating how the piston can beanchored to its rod at the extreme end thereof;

F IG. 5 is a view similar to FIG. 1 but illustrating another embodimentof the invention;

FIG. 6 is a cross sectional view taken on the line 6-6 of FIG. 5 andFIG. 7 is a sectional view similar to FIG. 5 but showing a furthermodification of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now more particularlyto the drawings, the numeral 10 designates a portion of the wall of ahydraulic cylinder 11 which houses an assembly 12 comprising an axiallyreciprocable piston rod 13, and a piston 14 carried by the inner endportion of the rod. The piston 14 is provided by a metal annulus orsleeve which substantially closely encircles the rod 13 and is confinedin the space 15 between the rod and the wall 10 ofthe cylinder.

As is customary, the piston 14 must have sealing engagement with theexterior of its rod 13 and with the inner surface of the cylinder wall10 along which it slides during extension and retraction of the pistonrod. Hence, at least one O-ring seal 16 is interposed between theexterior of the rod and the bore of the piston 14, with the sealconfined in a circumferential groove in one of said parts to preventleakage of fluid past the piston along the exterior of the rod.

Sealing of the piston along the cylinder wall can be effected by meansof piston rings, or by means of an annular V-section sealing member 17seated on the piston, and shown somewhat diagrammatically in FIGS. 1 and4. One end of the sealing member abuts an upstanding circumferentialflange 18 on the piston.

Near its opposite end, the piston of the FIG. 1 embodiment of theinvention is provided with a circumferential groove 19 that opens to itsperiphery and defines an upstanding annular flange 20 at the extremityof the piston. Though the piston has a substantially close fit on theexterior of its rod 13, it must nevertheless be firmly anchored theretoso as to assure against axial movement of the piston relative to therod. For that purpose, a single annular retainer 22 is provided. Theretainer encircles the rod and cooperates with the groove 19 and flange20 on the piston, and also with a grooved portion 23 on the rod todrivingly connect the piston thereto.

The retainer 22 is in the form of a circumferentially interruptedannulus, or split ring here shown as severed along a diameter thereof,as at 24, and having its periphery contiguous to the cylinder wall. Itthus comprises two complementary halves 25 which, in the present case,are identical. The ring halves are laterally displaceable off of the rod13 to opposite sides thereof, but they are normally held against suchdisplacement by the surrounding cylinder wall. A circumferentiallyinterrupted band 26 of bearing material can be snapped into a shallowgroove 27 in the periphery of the split ring, if desired, to not onlyprevent scoring of the cylinder wall but to also hold the ring in anoperative condition encircling the rod prior to insertion of theassembly into the cylinder.

The split ring halves are applied to the rod with a concentricsemicircular rib 28 on the interior of each engaging in the groovedportion 23 of the rod to hold the retainer against axial movementrelative to the rod. A radially inwardly directed annular flange 29provided on one axial end of the ring and which engages in the groove 19of the piston can then anchor the latter to the rod. The flange 29 isdefined by a radially inwardly opening circumferential groove 30 in thering, of a depth and width to snugly receive the flange 20 on thepiston.

The purpose of the grooved portion 23 of the rod, which can extendentirely around the rod, is to provide spaced apart abutments havingsurfaces 32 and 33 which oppose one another and face in opposite axialdirections. Similarly, it can be said that the groove 19 in the pistondefines other abutments having surfaces 34 and 35 which face in oppositeaxial directions. The retainer 22 is inter-connected with the rod andpiston abutments by its ribs 28 and by the flange 29 in such a way as toprovide an axial thrust transmitting connection between the piston andthe rod which can be maintained as long as the assembly is in placewithin the cylinder, but which connection is readily disruptable uponlateral displacement of the split ring halves from the rod after theassembly is removed from the cylinder.

To be effective for the transmission of the axial thrust from the pistonto the rod, the ribs on the ring halves should substantially closely fitthe groove 23 in the rod. In other words, the sides of the ribs shouldbe in axial thrust transmitting relation with the surfaces 32-33 on therod abutments. For the same reason, the flange 29 on the ring shouldsubstantially closely fit the groove 19 in the piston and thus be inaxial thrust transmitting relation to the surfaces 34-35 of itsabutments. Alternatively, axial thrust can be transmitted from thepiston to the split ring through the opposite sides of the piston flange20 and the opposing sides of the groove 30 in which the flange isreceived, as seen in FIG. 4. In this respect, it should also be notedthat the split ring 22 can be engaged by the adjacent end of the pistonsleeve 14 to provide a thrust transmitting connection between saidmembers effective to move the rod to the right as seen in FIG. 1 whenforce is applied to the left hand end of the piston. These directionsare the reverse in the FIG. 4 embodiment of the invention.

With the piston mounted close to but spaced from the inner end of itsrod 13 as seen in FIG. 1, the circumferential groove 23 must be formedin the rod a distance from its extremity; and the grooved and flangedend of the piston can be located directly alongside the groove 23.However, it will be appreciated that the piston can be mounted anywherealong the length of the rod merely by cutting a groove in the rodadjacent to the desired piston location.

This invention also permits mounting of the piston at the extreme innerend of the rod, to thereby give the advantage of the longest possiblestroke of the piston and rod assembly. Location of the piston at theextremity of its rod was impossible heretofore, wherever the piston wasfitted on a reduced and threaded end portion of the rod and clampedaxially between a shoulder at the base of the reduced end of the rod anda nut threaded thereonto. Consequently, the piston could never approachany closer to the end of the cylinder than was permitted by the nutholding it on the piston rod.

When the piston is mounted at the extremity of its rod, as seen in FIG.4, the split ring retainer 122 is placed at the end of the piston 114remote from the extremity of the rod. Its ribs 128, of course, similarlyengage the opposing surfaces 132-133 of abutments defined by acircumferential groove 123 in the rod.

Both of the embodiments described thus far feature anchoring of anannular piston on the piston rod of a cylinder by means of a split ringretainer that seats on and is supported by the piston rod. In bothcases, the end of the split ring retainer remote from the piston iscounterbored to provide an internal cylindrical wall 40 which engagesaround the exterior of the rod adjacent to the groove therein.

In the embodiment of the invention seen in FIG. 5, however, the splitring retainer 222 has a larger counterbore therein to define an internalcylindrical wall 43 that engages over the piston sleeve 214 to besupported by the latter. In this case also, the piston 214 differssomewhat from those described earlier in that it extends over the groove223 in the end portion of the piston rod 213 and a distance beyond theaxially opposing surfaces 232-233 of the groove. It is for this reasonthat openings 44 are formed in the sleeve, at diametrically oppositelocations in register with the groove 223, to enable a lug 228 on eachring half to pass down into the groove 223 through said openings 44. Thespacing between the axially opposed sides 4546 of the openings can beapproximately the same as the axial dimension of the groove 223 in therod, in order for the lugs 228 to properly anchor the piston to the rod.

The lugs 228 on the split ring retainer 222 do not complement oneanother in the provision of a substantially annular rib as is the casein the previously described embodiments. Instead, they extend radiallyinwardly toward one another from diametrically opposite portions of theretainer, at opposite sides of the diameter along which the ring issplit. In addition, the circumferential ends of the lugs can be formedto converge substantially radially inwardly, as shown, to facilitate theapplication of the complementary ring halves to the rod as well as theirdisplacement from the rod.

FIG. 7 indicates how an annulus 314, which may also be in the nature ofa piston, can be anchored to the piston rod 313 by means of a split ringretainer 322 like that seen in FIG. 5, wherein the retainer seats uponand is supported by the annulus 314. As therein shown, however, theannulus has an upstanding circumferential flange 50 at one end toconfine the split ring axially between it and the other end portion ofthe annulus.

Also, the openings in the annulus can be slightly larger, so that thering has thrust transmitting engagement with only the edges 145 of theopenings; while the engagement between the split ring and the flange 50provides for transmission of thrust in the opposite direction.

In all of the embodiments shown, it will be appreciated that thecircumferentially interrupted annular retainer can have the pistonmember formed as an integral part thereof and thus similarly comprisedof complementary piston sections. In this case, piston rings or othersealing means encircling the piston member and seated in grooves in itsperiphery can hold the circumferentially interrupted parts pre-assembledon the rod.

From the foregoing description, together with the accompanying drawings,it will be apparent to those skilled in the art that this inventionprovides a unique self-securing piston and rod assembly for a cylinderfeaturing anchoring of the piston to the rod by means of a singlecircumferentially interrupted retainer.

Those skilled in the art will appreciate that the invention can beembodied in forms other than as herein disclosed for purposes ofillustration.

The invention is defined by the following claims:

1. A piston and rod assembly for a cylinder, characterized by:

A. annular means encircling the rod and defining a piston adapted forsliding and sealing engagement with the wall of a cylinder for which theassembly is intended;

B. first and second abutment means on the rod and piston, respectively,each said abutment means having surfaces facing in opposite axialdirections;

C. an annular retainer encircling the rod and portions of the piston ata location adjacent to said second abutment means and having a diametersubstantially equal to that of the piston, said retainer beingcircumferentially interrupted to provide for lateral displacementthereof from an operative position encircling the rod; and

D. means on the retainer projecting inwardly therefrom toward the rodand interconnecting with said first and second abutment means, in axialthrust transmitting engagement with said surfaces thereof, to hold thepiston against axial movement relative to the rod.

2. The piston and rod assembly of claim 1, further characterized by:

A. the piston comprising a sleeve having diametrically opposite openingsin its wall providing said abutment means on the piston;

B. the rod having a grooved portion which registers with said openingsin the sleeve to provide said abutment means on the rod;

C. the retainer encircling and being supportingly seated on said sleeve;and

D. lugs on the retainer projecting inwardly therefrom and engaged insaid holes and in the grooved portion of the rod to provide saidinterconnecting means on the retainer.

3. The piston and rod assembly of claim 1, wherein the retainerencircles one portion of the piston and is axially confined betweenother portions of the piston.

4. A piston and rod assembly for a cylinder, characterized by:

A. means providing an annular piston which encircles the rod and has oneaxial end disposed substantially flush with one extremity of the rod;

B. an annular retainer encircling the rod adjacent to the other end ofthe piston, said retainer being circumferentially interrupted to providecomplementary arcuate sections which are laterally displaceable from therod but are adapted to be held against such displacement by the wall ofa cylinder for which the assembly is intended; and

C. means on the retainer interconnected in axial thrust transmittingengagement with portions of the rod and the piston to hold the latteragainst axial movement relative to the rod.

5. A piston and rod assembly for a cylinder, characterized A. annularmeans encircling the rod and defining a piston adapted for sliding andsealing engagement with the wall of a cylinder for which the assembly isintended;

B. first and second abutment means on the rod and piston, respectively,each said abutment means having surfaces facing in opposite axialdirections;

C. said second abutment means being defined by a groove in the pistonopening to its periphery adjacent to one end of the piston;

D. an annular retainer encircling the rod at a location adjacent to thepiston, said retainer seating on and being against axial movementrelative to the rod, said last named means comprising an internal flangeon the retainer extending into and filling said groove in the piston.

1. A piston and rod assembly for a cylinder, characterized by: A.annular means encircling the rod and defining a piston adapted forsliding and sealing engagement with the wall of a cylinder for which theassembly is intended; B. first and second abutment means on the rod andpiston, respectively, each said abutment means having surfaces facing inopposite axial directions; C. an annular retainer encircling the rod andportions of the piston at a location adjacent to said second abutmentmeans and having a diameter substantially equal to that of the piston,said retainer being circumferentially interrupted to provide for lateraldisplacement thereof from an operative position encircling the rod; andD. means on the retainer projecting inwardly therefrom toward the rodand interconnecting with said first and second abutment means, in axialthrust transmitting engagement with said surfaces thereof, to hold thepiston against axial movement relative to the rod.
 2. The piston and rodassembly of claim 1, further characterized by: A. the piston comprisinga sleeve having diametrically opposite openings in its wall providingsaid abutment means on the piston; B. the rod having a grooved portionwhich registers with said openings in the sleeve to provide saidabutment means on the rod; C. the retainer encircling and beingsupportingly seated on said sleeve; and D. lugs on the retainerprojecting inwardly therefrom and engaged in said holes and in thegrooved portion of the rod to provide said interconnecting means on theretainer.
 3. The piston and rod assembly of claim 1, wherein theretainer encircles one portion of the piston and is axially confinedbetween other portions of the piston.
 4. A piston and rod assembly for acylinder, characterized by: A. means providing an annular piston whichencircles the rod and has one axial end disposed substantially flushwith one extremity of the rod; B. an annular retainer encircliNg the rodadjacent to the other end of the piston, said retainer beingcircumferentially interrupted to provide complementary arcuate sectionswhich are laterally displaceable from the rod but are adapted to be heldagainst such displacement by the wall of a cylinder for which theassembly is intended; and C. means on the retainer interconnected inaxial thrust transmitting engagement with portions of the rod and thepiston to hold the latter against axial movement relative to the rod. 5.A piston and rod assembly for a cylinder, characterized by: A. annularmeans encircling the rod and defining a piston adapted for sliding andsealing engagement with the wall of a cylinder for which the assembly isintended; B. first and second abutment means on the rod and piston,respectively, each said abutment means having surfaces facing inopposite axial directions; C. said second abutment means being definedby a groove in the piston opening to its periphery adjacent to one endof the piston; D. an annular retainer encircling the rod at a locationadjacent to the piston, said retainer seating on and being supported bythe rod, and being circumferentially interrupted to provide for lateraldisplacement thereof from an operative position encircling the rod; andE. means on the retainer interconnecting with said groove and firstabutment means, in axial thrust transmitting engagement with saidsurfaces thereof, to hold the piston against axial movement relative tothe rod, said last named means comprising an internal flange on theretainer extending into and filling said groove in the piston.